Documents U.S. Pat. Nos. 3,744,745 and 4,685,643 disclose wake-control devices which are designed to act on the vortex trail generated on the wing of an airplane by a jet engine nacelle mounted under this wing. These conventional control devices comprise at least one control means which is arranged directly on the nacelle on one side thereof. This control means is distant from the leading edge of the corresponding wing and situated upstream of this leading edge. In addition, this conventional control means has an elongate shape, its longitudinal axis being substantially parallel to a local fluid flow and its upstream end possibly being pointed.
A conventional control means such as this generates an additional vortex intended to control the vortex trail.
This additional vortex has therefore to travel as far as the wing if it is to be able to act on said vortex trail that is to be controlled. Now, since the distance between this control means and said vortex trail is relatively great, it is difficult to find an appropriate position for said control means on the nacelle in order to lead the additional vortex precisely to the vortex trail. In addition, the path of this additional vortex varies generally according to the speed of the airplane and its angle of incidence.
Hence, in order to obtain a high-energy additional vortex which is able to act on said vortex trail irrespective of the situation, the control means described in the aforementioned documents have the shape of a flat plate, of very small thickness. It is known that a control means that has very angular edges (as is the case with such a plate) generates a powerful additional vortex and generally does so irrespective of the angle of incidence of the airplane. Because of the latter characteristic, a conventional control means does, nonetheless, have the disadvantage of also generating an additional vortex at airplane low angles of incidence, particularly in cruising flight, and this in particular leads to an unwanted increase in drag during this phase of the flight.
As a result, a conventional control device of the aforementioned type is not entirely satisfactory.
The present invention relates to a control device on the suction-face side of a lift-generating surface of an aircraft for controlling at least one vortex trail generated by at least one oblong element which is mounted under this lift-generating surface protruding partially beyond the leading edge of said lift-generating surface (particularly an airplane wing), in the upstream direction, which device provides a solution to the aforementioned disadvantages.